RXcetera

I've been searching this and everything I read says the fans should ALWAYS be on when the A/C is on and the blower is on, correct? Well when I turn the A/C on in my car, the fans come on for a bit, then I'm assuming the temps drop and the fans shut off again... while the A/C is still on. A minute or so later they will come on a again for a bit, then shut off again etc. Is this normal? If not, what would be causing this??

Kento

It's normal operation in milder temps at low cabin fan settings at idle. The A/C doesn't need to have the fans and/or compressor running constantly at that point.

RXcetera

So am I to understand that turning on the A/C tells the ECU to turn the fans on at a lower engine temp? And if so, what is this temp?

I always thought that turning the A/C on (when the fans arent normally running) should force the fans to run on at least low setting...

rynberg

Actually, according to the FSM, turning the A/C to ON should ALWAYS run the fans. The speed will vary with coolant temp.

RXcetera

That's what I thought... I checked all the relays and they are good. What else could be causing this?

DaleClark

iTrader: (55)

Turning the AC on kicks on one of the fan relays - the fan will always run with the AC on.

There are 3 fan speeds - low, medium, high. There are a number of inputs that will increase the fan speed - the thermoswitch, for example. Normally the fan is off until the thermoswitch kicks on or the ECU turns the fan on. With the AC on, the fan always runs at low, but if one or both of the other inputs kicks in, the speed will bump to medium or high.

Reason for the AC fan is the AC condensor (the AC "radiator" at the front of the car) always needs airflow over it to exchange heat to keep the AC cool.

Dale

RXcetera

As far as I can tell, all the fan speeds/sensors work properly. If I let the car sit, low speed will come on and turning on the A/C will yeild medium speed etc. If I start the car cold and turn on the A/C it will start the fans on low, but they will shut off after a bit, then come back on... So maybe the prob is the A/C? What would cause the A/C to cycle on and off (along with the fan)?

Kento

Hm, I don't have my FSM here with me, but I believe that turning on the A/C tells the ECU, which in turn activates the relays, according to its needs. My A/C behaves just like RXcetera's at idle when cold; at lower cabin fan speeds (settings 1 and 2), the fans will initially come on, but then shut off when the A/C air reaches a certain temp. They will cycle continually until the car warms up. I believe the A/C unit has a thermoswitch of some sort that reads the evaporator temp, and if it's low enough, shuts off the fans and even the compressor when necessary.

rynberg

That may be it Kento, I do know for a fact that the ecu blindly activates the relay to turn the fans on to low speed when the A/C is activated (higher speeds for higher temps,blah, blah). Perhaps there is another level of control from the A/C.

poss

iTrader: (5)

Mine are ALWAYS on with the A/C.

RXcetera

Shutting off the car, leaving the keys in the "on" position and turning on A/C will turn the fans on. Pulling the A/C relay and turning on the A/C will turn on the fans... so everything checks out. I had my A/C converted last year... maybe the pressure is too high/low and it's shutting down, who knows. I'm just suprised that when the A/C shutsdown, so do the fans.

DaleClark

iTrader: (55)

I just had my AC re-charged yesterday (long story) but for the past week or so I've been experimenting with the fans. With the AC system TOTALLY discharged and the compressor not running, if I switch the fan speed to any setting and turn on the AC button, the fans come on at low speed. They run ALL the time - cold, hot, etc.

Might have a loose connection in the circuit somewhere, which will be tricky to find. Could also be the fan relays, hard to say.

Anyhow, whether or not the AC works shouldn't have any impact on the fan itself.

Dale

Kento

The fact that your AC was totally discharged (and therefore unable to drop AC air temps) may have had something to do with it.

My AC has behaved this way since I've owned the car. It only occurs at idle (basically the only time whether you're going to be able to tell if the radiator fans are running anyway), and only on the lower two cabin fan settings; if I run anything higher, the radiator fans will usually stay on. Once the car warms up, it stops cycling. I haven't had any other issues with the fan relays, etc. For all we know, it could be related to the year, model, fan relay wiring update...who knows?

At this point, if the AC works fine and there are no other issues with the car, I wouldn't worry about it.